To support the specific aims of the Projects in this application, the Hematopathology Core will: 1. Provide the infrastructure for the procurement, evaluation, and banking of human germinal center B-cell lymphoma specimens. 2. Build a database for banked tumor specimens that includes pathologic, immunophenotypic, molecular genetic, and cytogenetic data. 3. Develop immunohistochemical methods for staining the protein products of genes identified by expression profiling of germinal center B-cell lymphomas. 4. Construct tissue arrays to study the protein products of prognostic markers and/or over-expressed genes in germinal center B-cell lymphomas. 5. Provide histology and immunohistology services for the evaluation of human germinal center B-cell lymphomas and their murine models. 6. Perform cytogenetic analyses to detect chromosomal translocations involving BCL2 and BCL6 in human B-cell lymphomas.